1.13 Principal Uranium-containing Minerals

At current prices of uranium ($30 to $50/lb U308) ores containing around 0.1 percent U308 or more are being mined primarily for their uranium content. The principal uranium-bearing minerals found in such ores are listed in Table 5.15, classified according to the type of treatment needed to extract the uranium.

The first group, minerals containing high concentrations of uranium, mostly in the tetravalent state, can be concentrated by specific gravity methods when in massive form. Frequently, however, the particle size is so small that the uranium-bearing mineral must be dissolved in sulfuric acid or sodium carbonate leach liquors. In either case, an oxidant must be added to bring uranium to the soluble, hexavalent state.

Uraninite, or pitchblende as it is more commonly known, is the form in which uranium was first discovered, at Joachimsthai, Czechoslovakia. Later, very rich deposits of massive uraninite were discovered at the Shinkolobwe mine in the Belgian Congo (Zaire) and were the principal source of uranium for the Manhattan Project. Leaner ores containing finely divided

Table 5.15 Principal uranium minerals

uraninite are now being mined in the Lake Athabasca district of Canada, in the White Canyon and Big Indian Wash districts of Utah, and the Jackpile mine of New Mexico.

Coffmite is a major mineral in the important Ambrosia Lake district of New Mexico. Uranothorite is mined in the Bancroft district of Ontario.

The second group of minerals in Table 5.15, hydrated minerals containing hexavalent uranium, are usually soft, finely divided, of relatively low density, and readily soluble in dilute sulfuric acid or sodium carbonate solution. Their uranium cannot be concentrated by specific gravity or flotation methods and must be recovered by leaching and concentration by selective precipitation, solvent extraction, or ion exchange. These ores are usually of secondary origin, precipitated from uranium-bearing groundwaters.

Camotite is a major ore of the Colorado plateau. Tyuyamunite occurs near Grants, New Mexico, in Utah, and in the Soviet Union. Autunite is found near Marysvale, Utah, and in Washington and Wyoming. Torbemite is found in the White Canyon district of Utah and in the upper zones of ore bodies in Zaire.

Minerals of the third group of Table 5.15 contain relatively small proportions of tetravalent uranium combined with a refractory oxide of titanium, niobium, or tantalum. To free the uranium from these minerals, they must be leached with hot, concentrated sulfuric acid. Davidite is one of the principal ores at Radium Hill in South Australia. Brannerite is found in the Blind River district of Ontario. Pyrochlore occurs in the Lake Nipissing district of Ontario and in Nigeria.